The Internet is a global system of interconnected computer networks. The Internet carries various information resources and services, including the World Wide Web (WWW). The WWW is a client-server model that includes web servers that provide access to documents via Hypertext Transfer Protocol (HTTP). Documents on the web servers are identified using Uniform Resource Locators (URLs). The documents and other content provided by web servers can be accessed by clients by way of a web browser application.
The documents and other content can include web pages or web applications created using Hyper Text Markup Language (HTML) or other markup languages. Some web browsers are capable of rendering web pages or web applications in a certain way using one or more Cascading Style Sheets (CSS) referenced by the web pages or web applications.
Web browsers commonly implement a global zoom function. This function affects all of the elements on a web page simultaneously and proportionally, for example, by scaling all of the text and images on a web page by a scaling factor. One way of implementing this is to provide a menu button or command that allows the user to select a global scaling factor. Another way of implementing this, on touch screen devices, is by scaling the web page according to the relative motion of two touch points. Because the screen size of the many touch screen devices, such as mobile phones or tablet computers, is limited, global zoom functions are commonly used.